In many parts of the United States, rainfall is insufficient and/or too irregular to keep turf and landscaping green and therefore irrigation systems are installed. Such systems typically include a plurality of underground pipes connected to sprinklers and valves, the latter being controlled by an electronic irrigation controller. One of the most popular types of sprinklers to cover large areas of landscape is the pop-up rotor-type sprinkler. In this type of sprinkler a tubular riser is normally retracted into an outer cylindrical case by a coil spring. The case is buried in the ground and when pressurized water is fed to the sprinkler the riser extends telescopically in an upward direction. A turbine and a gear train reduction are mounted in the riser for rotating a nozzle turret at the top of the riser. The gear train reduction is sometimes encased in its own sub-housing which is referred to as a gear box. A reversing mechanism is also normally mounted in the riser along with an arc adjustment mechanism which is used to manually set the arc of coverage of the sprinkler nozzle.
The gear drive of a rotor-type sprinkler can include a series of staggered gears and shafts wherein a small gear on the top of the turbine shaft drives a large gear on the lower end of an adjacent second shaft. Another small gear on the top of the second shaft drives a large gear on the lower end of a third shaft, and so on. Alternately, the gear drive can comprise a planetary arrangement in which a central shaft carries a sun gear that simultaneously drives several planetary gears on rotating circular partitions or stages that transmit reduced speed rotary motion to a succession of similar rotating stages. It is common for the planetary gears of the stages to engage corresponding ring gears formed on the inner surface of the housing. See, for example, U.S. Pat. No. 5,662,545 granted to Zimmerman et al.
Rotor-type sprinklers can be designed to wet a full circle area around the sprinkler, or just part of a circle in which case an arc of pre-set angular dimension is covered by the stream of water ejected from the nozzle. Rotor-type sprinklers typically include at least one removable nozzle. Nozzles are typically available that change the amount of water being applied in terms of gallons per minute (GPM) and the radius or reach of the area being irrigated. The nozzle is installed into a cylindrical nozzle turret which is rotated at the top of the riser by the gear drive mechanism. The nozzle turret has at least one nozzle port where the nozzle is inserted. See for example U.S. Pat. No. 5,699,962 granted Dec. 23, 1997 to Loren W. Scott et al. and assigned to Hunter Industries, Inc. the assignee of the subject application. The nozzle port is typically inclined to cause the stream of water ejected from the nozzle to be sent upwards and outwards from the sprinkler. It is common for the port in the nozzle turret to be inclined at about twenty-five degrees relative to the surface of the surrounding landscape.
There are times when the sprinkler is installed in a landscape area where there is a hill in front of the sprinkler that may interfere with the stream of water spraying out of the sprinkler. It is common for an installer to install the sprinkler at an angle to the horizon to allow the sprinkler to shoot over the hill. This may require an additional sprinkler to irrigate the flat area in front of the hill. Other times, the sprinkler may be installed in an area with wind that carries the water off if it is emitted at too high of an angle. Manufactures often supply specially design low angle nozzles for this application that cause the stream to exit the sprinkler at a lower trajectory. A lower trajectory may also be required if low overhanging vegetation like tree limbs get in the way of a high trajectory and interfere with the irrigation process.